Turbine engines that are used in the electric power generation industry typically include a plurality of combustors which are arranged concentrically around an input to the turbine section. A typical combustor assembly is shown in FIG. 1. The combustor assembly includes both primary and secondary fuel nozzles.
The primary and secondary fuel nozzles inject fuel into a flow of compressed air received from the compressor side of the turbine. The fuel is mixed with the air, and the fuel-air mixture is then ignited downstream from the fuel injectors in one or more combustion zones. Ideally, the combustion takes place at a location that is located downstream from the distal ends of the fuel nozzles so that the nozzles themselves are not subjected to extremely high temperatures. In addition, it is common for fuel nozzles to include purge air passageways which conduct a flow of the compressed air that is designed to cool the nozzles.
During some turbine operational conditions, the purge air passageways of the fuel nozzle are temporarily prevented from conducting a flow of cooling air. In those instances, portions of the fuel nozzles adjacent the combustion zones can be subjected to extremely high temperatures that can damage the fuel nozzles. Typically, the downstream ends of the nozzles are subjected to the highest temperatures, and are therefore most likely to be damaged.